Methods for forming amorphous ultra-high molecular weight polyalphaolefin drag reducing agents using non-metallocene catalysts and alkylaluminoxane

ABSTRACT

A composition including polyalphaolefins that function as drag reducing agents and a process for the preparation of polyalphaolefins that function as drag reducing agents are disclosed. The process includes contacting alpha olefin monomers with a catalyst system, which includes a catalyst and an activator (co-catalyst) in a reactant mixture. The catalyst is a transition metal catalyst, preferably titanium trichloride, and the co-catalyst may include an alkylaluminoxane, alone or in combination, with a dialkylaluminum halide or a halohydrocarbon. The polymerization of the alpha olefin monomers produces a non-crystalline, ultra-high molecular weight polyalphaolefin having an inherent viscosity of at least 10 dL/g. The addition of the alkylaluminoxane during the polymerization process provides for a non-crystalline, ultra-high molecular weight polyalphaolefin and a more uniform molecular weight distribution of the resulting polyalphaolefin, thereby creating a drag reducing agent superior to known drag reducing agents. A process for forming a drag reducing agent comprising a non-crystalline, ultra-high molecular weight polyalphaolefin having an inherent viscosity of about at least 10 dL/g and a process for reducing drag in a conduit are also disclosed.

This application is a continuation application of U.S. application Ser.No. 09/081,964 filed May 20, 1998, now U.S. Pat. No. 6,015,779, which isa continuation-in-part of U.S. application Ser. No. 08/619,840, filedMar. 19, 1996, now U.S. Pat. No. 5,869,570.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to methods for improving flow of hydrocarbonsthrough conduits. particularly pipelines. The invention also relates tomethods for making improved drag reducing agents, and preferably, tomethods for making ultra-high molecular weight amorphous polymers andcopolymers of alpha olefins with improved drag reducing properties,having inherent viscosities in excess of about 10 dL/g.

2. Description of Related Art

Generally speaking, the flow of liquid in a c onduit, such as apipeline, results in frictional energy losses. As a result of thisenergy loss, the pressure of the liquid in the conduit decreases alongthe conduit in the direction of the flow. For a conduit of fixeddiameter, this pressure drop increases with increasing flow rate. Whenthe flow in the conduit is turbulent (Reynold's number greater thanabout 2100), certain high molecular weight polymers can be added to theliquid flowing through the conduit to reduce the frictional energylosses and alter the relationship between pressure drop and flow rate.These polymers are sometimes referred to as drag reducing agents(“DRAs”), and they interact with the turbulent flow processes and reducefrictional pressure losses such that the pressure drop for a given flowrate is less, or the flow rate for a given pressure drop is greater.Because DRAs reduce frictional energy losses, increase in the flowcapability of pipelines, hoses and other conduits in which liquids flowcan be achieved. DRAs can also decrease the cost of pumping fluids, thecost of equipment used to pump fluids, and provide for the use of asmaller pipe diameter for a given flow capacity. Accordingly, an ongoingneed exists to formulate improved drag reducing materials.

While various polymerization methods and reactants have been publishedin the patent literature, most of those methods do not yield specializedpolymers with properties that make them effective as drag reducers. Manyof the methods, for example, produce non-amorphous polymers, e.g., solidor crystalline polymers. Other methods yield polymers with molecularweights that are much too low to be useful in drag reduction. Stillother methods yield polymers having poor drag reducing properties. Forexample, some commercially available polymers are deficient when usedwith highly viscous crude oil, where the need may be the greatest. Incertain aspects, the present invention overcomes one or more of theabove-mentioned shortcomings.

While alkylaluminoxane has been used in certain polymerizationprocesses, the inventors are not aware of any patents or publicationsshowing alkylaluminoxane being used to make drag reducing agents (DRAs)in general, or, more specifically, to make amorphous, ultra-highmolecular weight polyalphaolefin polymers with the superior dragreducing properties of the present invention. For example, U.S. Pat.Nos. 5,436,212; 5,298,579; 5,070,160 and 4,659,685 disclose certain usesof alkylaluminoxane, but do not disclose or suggest the presentinvention.

SUMMARY OF INVENTION

The present invention is directed to methods of improving the flow ofhydrocarbons through conduits, particularly viscous crude oil flowingthrough pipelines. Surprisingly, it has been discovered that a dragreducing agent (DRA) made in accordance with the methods of thisinvention can produce as much as about thirty percent (30%) or greaterflow improvement when added to a hydrocarbon flowing through a conduit.Advantageously, such flow improvement can result when the drag reducingagent's polymer is added to the hydrocarbon at a concentration of as lowas 1 part per million (ppm) by weight.

In certain aspects, the invention also relates to methods of producingamorphous, ultra-high molecular weight drag reduction agents havingunexpectedly superior drag reduction properties when combined withliquid hydrocarbons, such as viscous crude oil. In another aspect, theinvention is directed to a composition of matter, including an amorphousdrag reduction agent with an ultra-high average molecular weight, far inexcess of ten million, with inherent viscosities in excess of about 10dL/g.

Broadly, one aspect of the invention involves a method of producing anamorphous polyalphaolefin mixture containing an ultra-high molecularweight polyalphaolefin polymer with an inherent viscosity of at leastabout 10 dL/g and surprisingly superior drag reducing properties whencombined with crude oil that is flowing through a pipeline or otherconduit. The method preferably includes the steps of contacting areactant mixture that includes alpha olefin monomers with a transitionmetal catalyst and an alkylaluminoxane co-catalyst, to provide anamorphous polyalphaolefin mixture containing an ultra-high molecularweight polyalphaolefin polymer with an inherent viscosity of at leastabout 10 dL/g and surprisingly superior drag reducing properties whenused with viscous crude oil. The polyalphaolefin mixture can beintroduced to a pipeline or other conduit having flowing hydrocarbons,such as viscous crude oil. The polyalphaolefin DRA mixture should beintroduced in an amount sufficient to increase the flow of the flowinghydrocarbons, preferably at a concentration of from about 1 to 250 ppmby weight, and more preferably from about 25 to 150 ppm by weight.

A specific embodiment of the invention is directed to a method forforming a drag reducing agent comprising a non-crystalline, ultra-highmolecular weight polyalphaolefin having an inherent viscosity of atleast about 10 deciliters per gram, by contacting alpha olefin monomerswith a catalyst system that includes a transition metal catalyst and aco-catalyst mixture that includes an alkylaluminoxane co-catalyst; andpolymerizing the alpha olefin monomers at a temperature at about or lessthan about 25° C.; wherein, during the polymerization, at least aportion of the alpha olefm monomers polymerize in the reactant mixtureto provide an ultra-high molecular weight polyalphaolefin.

In another specific embodiment of the invention, the polymerization isterminated by adding a “deactivator” to the reactant mixture after atleast a portion of the alpha olefin monomers polymerize in the reactantmixture, to provide an amorphous, ultra-high weight polyalphaolefin. Oneexample of a deactivator is a mixture of isopropyl alcohol and butylatedhydroxytoluene.

A variety of alpha olefin monomers are useful in this invention,including homopolymers, copolymers and terpolymers, which can be presentin the reactant mixture in different amounts, alone or in combination.Preferably, these monomers are present at a charge rate of about 4% to22% based on total weight of the reactant mixture. Charge rate is hereindefined as the weight percent of total charge including solvent,co-catalyst, catalyst, and alpha olefin monomers. More preferably, thesemonomers are present at a charge rate of 8% to 20% based on total weightof the reactant mixture. Examples of alpha olefin monomers that areuseful in this invention are co-polymers of 1-hexene and 1-dodecenealpha olefins; or co-polymers of I-octene and 1 -tetradecene alphaolefins in a 1:1 ratio based upon mole weight of the monomers.

A preferred transition metal catalyst is titanium trichloride, which ispreferably present in the reactant mixture in an amount of from about100 to about 1500 parts per million, preferably from about 150 to about400 parts per million, based on the total weight of all the reactants orcomponents in the reactant mixture.

A further feature of the process for forming a drag reducing agentcomprising a non- crystalline, ultra-high molecular weightpolyalphaolefin having an inherent viscosity of at least about 10deciliters per gram is that the reactant mixture may include at leastone hydrocarbon solvent such that the alpha olefin monomers andpolyalphaolefin remain substantially dissolved in the hydrocarbonsolvent. An additional feature of the process is that the polymerizationof the alpha olefin monomers continues such that the polyalphaolefin ispresent in the reactant mixture at a concentration of at least about 4weight percent based upon the weight of the reactant mixture and thepolyalphaolefin having an inherent viscosity of at least about 10deciliters per gram is formed in less than about 12 hours. Anotherfeature of the process is that the polyalphaolefin has an inherentviscosity of at least about 10 deciliters per gram and is amorphous withsubstantially no crystalline particles. A further feature of the processis that the flow increase is at least about 30% when the polyalphaolefinis present in hexane at a weight concentration of 1 part per million.Another feature of the process is that the catalyst system may includedibutylaluminum chloride and/or diethylaluminum chloride.

In another specific embodiment, the present invention includes a dragreducing agent comprising a non-crystalline, ultra-high molecular weightpolyalphaolefin having an inherent viscosity of at least 10 decilitersper gram, formed by contacting alpha olefin monomers with a catalystsystem in a reactant mixture, wherein the catalyst system includes atransition metal catalyst, such as titanium trichloride, and theco-catalyst mixture includes an alkylaluminoxane co-catalyst, such asmethylaluminoxane and isobutylaluminoxane; and polymerizing the alphaolefin monomers at a temperature at about or less than 25° C.,preferably less than 10° C., wherein during the polymerization, at leasta portion of the alpha olefin monomers polymerize in the reactantmixture to provide a non-crystalline, ultra-high molecular weightpolyalphaolefin.

In yet another specific embodiment, the present invention includes aprocess for reducing drag in a conduit by forming a drag reducing agentcomprising a non-crystalline, ultra-high molecular weightpolyalphaolefin, by contacting alpha olefin monomers with a catalystsystem in a reactant mixture, wherein the catalyst system includes atransition metal catalyst and an alkylaluminoxane co-catalyst;polymerizing the alpha olefin monomers at a temperature at about or lessthan 25° C., preferably less than 10° C.; wherein during thepolymerization, at least a portion of the alpha olefin monomerspolymerize in the reactant mixture to provide a non-crystalline,ultra-high molecular weight polyalphaolefin having an inherent viscosityof at least 10 deciliters per gram; and introducing the drag reducingagent into the conduit.

In still another aspect of the invention, a halohydrocarbon co-catalystmay be used in conjunction with a transition metal catalyst to form thedrag reducing agent. For example, another specific embodiment of theinvention is directed to a process for forming a drag reducing agentcomprising a non-crystalline, ultra-high molecular weightpolyalphaolefin having an inherent viscosity of at least about 10deciliters per gram. The process includes the steps of contacting alphaolefin monomers with a catalyst system in a reactant mixture, whereinthe catalyst system includes a transition metal catalyst and aco-catalyst mixture having at least two co-catalysts, wherein one of theco-catalysts preferably is a halohydrocarbon. More preferably, theco-catalyst mixture also includes alkylaluminoxane. The alpha olefinmonomers are polymerized at a temperature at about or less than 25° C.,wherein during the polymerization, at least a portion of the alphaolefin monomers polymerize in the reactant mixture to provide anon-crystalline, ultra-high molecular weight polyalphaolefin.

A further feature of the process for forming a drag reducing agentcomprising a non- crystalline, ultra-high molecular weightpolyalphaolefin having an inherent viscosity of at least about 10deciliters per gram is that the halohydrocarbon is preferably a chloridecontaining halohydrocarbon such as ethylene dichloride. Another featureof the process is that the transition metal catalyst is preferablytitanium trichloride. An additional feature of the process is that thecatalyst system preferably includes an alkylaluminoxane such asmethylaluminoxane and/or isobutylaluminoxane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of a single-stage batch process.

FIG. 2 is a flow diagram of a single-stage continuous process.

FIG. 2 is a flow diagram of a two-stage continuous process.

FIG. 4 is a DRA Performance Curve.

FIG. 5 is another DRA Performance Curve.

FIG. 6 is a comparative DRA Performance Curve.

FIG. 7 is another comparative DRA Performance Curve.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description refers to certain details andspecific aspects of the invention, including specific embodiments andexamples of the invention. Also, for purposes of better understandingthe invention, certain terms will now be explained and defined. It is tobe understood that the invention is not limited or restricted to thespecific examples and embodiments described below, which are included toassist a person skilled in the art in practicing the invention. Rather,the scope of the invention is determined based on the claims below,including any equivalents thereof.

Drag Reducing Agents.

The term “drag reducing agent” (DRA) as used herein refers to acomposition that includes at least the formed polyalphaolefin polymer,preferably made in accordance with the methods described herein.Preferably, because the polyalphaolefin polymer of this invention istypically fully dissolved in the solvent, the “DRA” can also refer tothe entire reactant mixture after sufficient polymerization has occurred(also referred to as a “polymerization mixture”), including not only thepolyalphaolefin, but also the solvent, any viscosity reducing agents andany unreacted monomers. The DRA can also include any remainingtransition metal catalyst and cocatalyst. The term “polyalphaolefin”refers to the polymer material formed by the polymerization of the alphaolefin monomers, and is broadly construed to include not only thepolymer in its final form, e.g., polyalphaolefin having an ultra-highmolecular weight and inherent viscosity of 10 dL/g or greater, but alsoany intermediate polymers being formed, sometimes referred to as“oligomers.”

Flow Increase.

A preferred aspect of the present invention is directed to “flowincrease” or “drag reduction.” As discussed below, drag reducing agentsreduce drag and increase the flow rate of hydrocarbons passing throughconduits, particularly crude oil or refined hydrocarbons passing throughpipelines. In at least one aspect, the DRA can be introduced into theconduit to improve flow conditions by reducing frictional pressurelosses, or frictionally generated energy bursts, associated withmovement of fluid within the conduit. These frictionally generatedeniergy bursts typically emanate from throughout the turbulent core ofthe flowing hydrocarbons and include lateral turbulent microburstsgenerated from or near the conduit walls. More simply stated, the DRAstend to reduce the impact of turbulence through direct interaction andabsorption of some or most of these energy bursts thus improving flowcharacteristics in the conduit. It has been discovered that a DRA shouldhave the right combination of properties to provide superior dragreduction and flow improvement. For example, the DRA should benon-crystalline and amorphous, preferably having substantially no solidparticles. The DRA also should have an ultra-high molecular weight, asdiscussed above. Finally, the DRA needs to provide superior flowimprovement. In this respect, it has been observed by the inventors thatthe mere fact that a polymer is amorphous and has a very high molecularweight does not necessarily make it useful for flow improvement. Thesuperior properties of the DRA of this invention are thus bothsurprising and unexpected.

Accordingly, one of the more important aspects of the invention is thesuperior “flow increase” or “drag reduction” provided by the DRA Thatis, when combined in sufficient quantities with a hydrocarbon flowingthrough a conduit, the DRA of this invention provides a flow increasethat is superior to the flow increases provided by other commerciallyavailable DRAs. Although flow increase can be defined in qualitativeterms, it can also be quantified, for comparison purposes, by using anempirical test sometimes called a “Percent Flow Increase” test,calculated using the following equation:${{Percent}\quad {Flow}\quad {Increase}} = {\frac{W_{1} - W_{0}}{W_{0}} \times 100\%}$

As discussed below in the Examples, Percent Flow Increase measurementswere taken of certain samples of invention DRA and also of certaincomparative DRA samples. Both 1″ and ¼″ diameter hydraulic flow loopswere used herein to measure Percent Flow Increase. The value “W₀” refersto the weight of a test sample of hydrocarbon without any DRA present,while the term “W₁” refers to the weight of a test sample of hydrocarbonwith a predetermined amount of DRA present. In either case, the weightof the test sample is determined by carefully weighing the amount ofhydrocarbon that passes through the flow loop over a constant timeinterval. The time interval is dependant upon the total weight of DRAtreated hydrocarbon which is passed through the flow loop. In the 1″flow loop, this weight is typically greater than 150 pounds of DRAtreated hydrocarbon. In the ¼″ flow loop, this weight is typically about1 pound of DRA treated hydrocarbon.

Similarly, another quantitative method of measuring drag reduction, andparticularly for comparing different DRAs, is measuring “Percent DragReduction” (%DR) which is calculated using the following equation:${{Percent}\quad {Drag}\quad {Reduction}} = {\frac{P_{1} - P_{0}}{P_{0}} \times 100\%}$

The term “P₀” refers to the measured pressure drop occurring when purehexane (without DRA) is pumped through a flow loop. The term “P₁” refersto the measured pressure drop occurring when hexane (treated with DRA)is pumped through the flow loop. Percent Drag Reduction (%DR) is alsodiscussed in the Examples.

Ultra-High Molecular Weight.

Another important aspect of this invention is that the polyalphaolefinpolymer must have an “ultra-high molecular weight,” a term definedherein as a molecular weight corresponding to an inherent viscosity ofat least about 10 dL/g. Because of the extremely high molecular weightof the DRA polymer, it is difficult to reliably and accurately measurethe actual molecular weight, but inherent viscosity provides a usefulapproximation of molecular weight. For purposes of the presentinvention, “inherent viscosity” is measured using a Cannon-Ubbelohdefour bulb shear dilution viscometer (0.1 g polymer/100 ml toluene at 25°C.). Inherent viscosities are calculated for each of the four bulbs. Theviscosities are then plotted as a function of shear rate. The plot isthen used to determine the inherent viscosity at a shear rate of 300sec-1. It is contemplated that an inherent viscosity of 10 dL/gcorresponds roughly to a molecular weight of at least about 10 or 15million. Preferably, the ultra-high molecular weight polyalphaolefins ofthe present invention have molecular weights even higher, e.g., greaterthan 25 million. The polyalphaolefins formed should also have a narrowmolecular weight distribution. Because different assumptions about theproperties of the polyalphaolefin can yield different estimates ofmolecular weights, the inventors prefer using inherent viscosity tocharacterize the molecular weights of their drag reducing agents.

Amorphous.

Yet another property of the polyalphaolefin made in accordance with theinvention is its substantially non-crystalline nature. Preferably, thepolyalphaolefin is liquid and is soluble in the hydrocarbon solvent usedas discussed herein, so that a single liquid phase reactant mixture isprovided. Preferably, the polyalphaolefin is amorphous, having nocrystalline structures, or habits, existing in a single phase withsubstantially no solid particles. Preferably, during the polymerizationprocess, the polyalphaolefin being formed fully dissolves into thesolvent, providing a single-phase DRA that can be used without the needto conduct any separation procedures. Furthermore, another advantage ofthe single-phase DRA of this invention is that it can be convenientlytested for quality purposes. Moreover, this DRA has a long stable shelflife.

Catalyst System.

An important aspect of the invention is the “catalyst system,” which, asdefined herein, includes a transition metal catalyst and a co-catalystmixture, preferably containing an alkylaluminoxane co-catalyst. Thetransition metal catalyst and the alkylaluminoxane co-catalyst can becombined with the alpha olefin monomer in a number of ways. Thetransition metal catalyst and alkylaluminoxane co-catalyst arepreferably combined with the monomer at the same time. They arepreferably mixed together before the polymerization reaction isinitiated. Preferred transition metal catalysts include catalystscontaining titanium trichloride, titanium tetrachloride or metalloceneor combinations thereof. Preferably, the transition metal catalysts arenon-metallocene. Titanium trichloride, which is most preferred, has beenused for years in making drag reducing agents, and is preferably used inan amount ranging from at least about 100 to 1500 parts per million(ppm) based on the weight of all the components, i.e., the alphaolefins, solvents, co-catalysts, and catalysts supplied to the reactor.The co-catalyst mixture may include alkylaluminoxane alone, or may alsoinclude at least one other component, such as diethylaluminum chloride(“DEAC”) or dibutylaluminum chloride (“DIBAC”). In a highly preferredaspect of the invention, other co-catalysts that provide excellentresults are halohydrocarbons, such as ethylene dichloride used eitheralone, or in combination with an alkylaluminoxane co-catalyst.

Alkylaluminoxane.

Surprisingly, it has been discovered that a component that provides thepolyalphaolefin of this invention with its superior flow improvingproperties when combined with hydrocarbons (e.g., crude oil) isalkylalumiinoxane, preferably either methylaluminoxanie (MAO) orisobutylaluminoxane (IBAO). Thus, alkylaluminoxane is a particularlycritical ingredient for carrying out the method of the invention.Alkylaluminoxane is a compound having a plurality of aluminum atoms,typically formed by a condensation reaction in which a trialkylaluminumcompound (e.g., trimethylaluminum) is combined with a condensing agent,such as water (i.e., resulting in hydrolysis). It is noted, however,that the present invention is not concerned with how to actually makethe alkylaluminoxane, which is commercially available from a variety ofsources, for example, AKZO NOBEL Chemical Inc., Chicago, Ill.

In addition to MAO and IBAO, it is contemplated that otheralkylaluminoxanes can also be used, including chain alkylaluminoxanesand cyclic aluminoxanes. A chain aluminoxane has the following generalstructure, wherein R¹ is an alkyl group and n is the polymerizationdegree:

A cyclic alkylaluminoxane is a long-chained compound having a chemicalstructure formed by repeating units having the following structure,wherein R¹ is an alkyl group:

In the method of the invention, the concentration of thealkylaluminoxane in the co-catalyst mixture is preferably in the rangeof at least about 100 to about 3500 parts per million (ppm), based onthe weight of all the components in the reactant mixture. Morepreferably, the concentration of the alkylaluminoxane in the catalystmixture is from at least about 800 to about 2000 ppm.

Halohydrocarbon.

Another surprising discovery relates to the use of one or morehalohydrocarbons as co-catalysts. “Halohydrocarbons” are herein definedas compounds having the formula R-X_(n), wherein X is a halogen, n isthe number of halogen atoms, and R is a hydrocarbon group such asaromatic and aliphatic hydrocarbons, including alkanes, alkenes,acetylenes, or any other hydrocarbon known to persons skilled in the artwhich may be combined with one or more halogens in accordance with theformula R-X_(n). In a specific embodiment, the X is chloride, n is 2.and R is an alkane. More preferably, the halohydrocarbon is ethylenedichloride.

Specifically, it has also been discovered that using a halohydrocarbonas a co-catalyst, particularly in combination with an alkylaluminoxaneco-catalyst, provides polyalphaolefins with superior flow improvingproperties when compared to other drag reducing agents. Chloridecontaining halohydrocarbons are preferred. Although only theoretical atthis point, it is contemplated that the chloride containinghalohydrocarbons act as chloride donors which promote polymerization ofalpha olefins.

The halohydrocarbon is preferably combined with an alkylaluminoxane andtitanium trichloride catalyst to form a catalyst system, e.g., a slurry.It is contemplated that, in a specific embodiment, dibutylaluminumchloride and/or diethylaluminum chloride may also be included in thecatalyst slurry. The catalyst system is then mixed with the alpha olefinmonomers. It has been discovered that polymerization of the alpha olefinmonomers in the presence of the halohydrocarbon forms a polyalphaolefinwhich has improved drag reducing capabilities.

Perhaps the most surprising result arising from the use of a co-catalystmixture utilizing both ethylene dichloride and alkylaluminoxane is itsimpact on polymerization rates. For example, typical Ziegler-Nattapolymerization processes require approximately 15 to 70 hours ofpolymerization time to form a weight percent polyalphaolefin having dragreducing characteristics. By comparison, using ethylene dichloride as aco-catalyst, the rate of polymerization is increased dramatically suchthat the weight percent of the polyalphaolefin in the reactant mixturemay be formed in less time. For example, a reactant mixture having aselected weight percent polyalphaolefin as a reference may be formed inunder 12 hours. Preferably, a 5 weight percent polyalphaolefin may beformed in under 7 hours, and more preferably, in under 5 hours. Such arapid rate of polymerization is a dramatic improvement over the currentprocedures for forming drag reducing agents.

In a specific embodiment of the invention, a drag reducing agentcomprising a non-crystalline, ultra-high molecular weightpolyalphaolefin having an inherent viscosity of at least about 10deciliters per gram is formed by contacting alpha-olefin monomers with acatalyst system in a reactant mixture. The catalyst system includes atransition metal catalyst, such as titanium trichloride, and aco-catalyst mixture having at least two co-catalysts, wherein one of theco-catalysts is a halohydrocarbon. While it is contemplated that anyhalohydrocarbon co-catalyst may be utilized, preferably, thehalohydrocarbon co-catalyst is either an alkyl halide or an alkyldihalide, and more preferably is an alkyl dihalide. Preferably thehalogen atom of the halohydrocarbon is chloride, and the most preferredhalohydrocarbon is ethylene dichloride. An alkylaluminoxane co-catalystsuch as methylaluminoxane and/or isobutylaluminoxane is preferablyincluded in the catalyst system.

The alpha olefin monomers should be polymerized at a temperature atabout or less than 25° C., and preferably, at about or less than 10° C.,wherein during the polymerization, at least a portion of the alphaolefin monomers polymerize in the reactant mixture to provide anon-crystalline, ultra-high molecular weight polyalphaolefin.Preferably, the alpha olefin monomers are polymerized at a temperatureof about −5° C. The ethylene dichloride co-catalyst should be present inthe reactant mixture at a concentration ranging from at least about 50weight ppm based upon the weight of all the reactants in the reactantmixture to about 200 weight ppm. Preferably, the ethylene dichloride ispresent in the reactant mixture at a concentration ranging from at leastabout 80 weight ppm to about 120 weight ppm.

Reactant mixture.

Generally, the reactant mixture includes alpha olefin monomers andsolvent, which is then combined with the “catalyst system,” discussedabove. Useful alpha olefin monomers broadly include any that are capableof forming a polyalphaolefin with the desired properties discussedherein. Preferably, the alpha olefins have 2 to 20 carbon atoms.Homopolymers, copolymers and terpolymers may be used. Preferred alphaolefins include ethylene, propylene, 1-butene, 4-methyl-1-pentene,1-hexene, 1-octene, 1-decene, 1-dodecene and 1-tetradecene; conjugatedor unconjugated dienes such as butadiene and 1,4-hexadiene; aromaticvinyls such as styrene; and cyclic olefins such as cyclobutene. Mostpreferably, the alpha olefin monomers are co-polymers of 1-hexene and1-dodecene present in a 1:1 mole ratio; or co-polymers of 1-octene and1-tetradecene present in a 1:1 mole ratio. The alpha olefin monomers canbe present in the reactant mixture at a charge rate of 4% to 22% basedupon the total weight of the reactant mixture, or more preferably, at acharge rate of 8% to 20%.

Polymerization.

Liquid phase polymerization is the preferred technique for forming theDRA polyalphaolefins of this invention, as discussed below in greaterdetail. In liquid phase polymerization, the monomers and polymers areboth completely dissolved in the solvent. It is critical thatsubstantially no solid phase particles are formed. It is contemplated,however, that a variety of other polymerization reactions can form theDRA polyalphaolefins of this invention, including, for example, gasphase polymerization, bulk polymerization, suspension polymerization andemulsion polymerization. These polymerization procedures are relativelyconventional, and are generally either known by persons skilled in theart; readily ascertainable from the patent and technical literature; orcan be arrived at without excessive experimentation. Additionally,either batch or continuous polymerization methods can be used, in eitherone or multiple stages. Furthermore, the various reactants may be addedto the reactant mixture in numerous ways, all which are known to personsskilled in the art. For example, the catalyst, alpha olefin monomers,and hydrocarbon solvent may be combined together in a storage tank andstored until the polymerization process is initiated by the addition ofthe co-catalyst mixture. Alternatively, the catalyst and the alphaolefins may be combined in advance of adding the hydrocarbon solvent andthe co-catalyst from separate sources. Preferably, as discussed below,the catalyst system including transition metal catalyst and one or moreco-catalysts is formed first and then combined with the alpha olefinmonomers and the hydrocarbon solvent from separate sources.

Batch liquid phase polymerization is part of a presently preferredmethod of forming the DRAs of this invention. Because relatively lowtemperatures are involved, insulated reaction vessels are used. Thetemperature of the reactant mixture is preferably maintained at about25° C. or less, preferably, at about 10° C. or less. The pressure of thereaction mixture is not critical, and is usually in the range of fromabout atmospheric pressure to about 1500 psig. The polymerization isconducted under conditions such that the polyalphaolefin being formedwill have an inherent viscosity of about at least 10 deciliters per gram(dL/g). The time for the polyalphaolefin to reach that inherentviscosity depends largely on the catalyst system, reaction conditionsand the concentration of monomers being polymerized.

A catalyst system can be prepared by first mixing the appropriate amountof transition metal catalyst (e.g., titanium trichloride) with therespective liquid co-catalysts. This catalyst system is then directed toa storage vessel where the catalyst system may be stored, or aged orconditioned, for a time sufficient to optimize the efficaciousness ofthe catalyst system. Preferably, the catalyst system is stored for atleast about 6 to about 72 hours. More preferably, the catalyst system isstored for at least about 10 to about 30 hours. To begin thepolymerization reaction, the catalyst system can be metered from thisstorage vessel into the first reactor where it is mixed in desiredproportions with the alpha olefin monomers.

In a batch process, polymerization can be initiated in a first reactorat an appropriate temperature and pressure. After polymerizationprogresses for a predetermined period of time, e.g., long enough to forma certain amount of polyalphaolefin polymer with a certain molecularweight and molecular weight distribution as determined by, e.g.,inherent viscosity, the polyalphaolefin mixture can be transferred to asecond reactor, where polymerization continues, until thepolyalphaolefin mixture has the desired final inherent viscosity viamonomer to polymer conversion. After this transfer takes place, freshstarting ingredients can be added to the first reactor, including newamounts of catalyst system containing alkylaluminoxane co-catalyst andunreacted alpha olefins.

Alternatively, two reactors can be used in a continuous process. Duringstart-up, the starting ingredients, i.e., the alpha olefin monomerreactants, a transition metal catalyst, co-catalyst mixture are added tothe first reactor. After a period of time, the monomers in the firstreactor form a predetermined minimum amount of oligomers andfully-formed polyalphaolefin polymers. A portion of the oligomers andpolymers are then continuously pumped into the second reactor, at apredetermined rate and mixed with a hydrocarbon solvent. The hydrocarbonsolvent enhances the ability of the DRA to become incorporated ordissolved into the hydrocarbons, e.g., the crude oil in a pipeline.While it is contemplated that any hydrocarbon solvent may be employedwhich enhances the DRA's incorporation into the hydrocarbon, suitablehydrocarbon solvents include aromatic and aliphatic hydrocarbons,butanes, propanes, isopentanes, and other mixed liquid propane gas andnatural gas liquids. Preferably, all acceptable solvents must notcontain more than trace amounts (i.e., less than about 5 ppm) of sulfuror sulfur containing compounds.

Simultaneously, new starting ingredients are pumped into the firstreactor, eventually reaching a steady state balance between the incomingingredients and the outgoing oligomer/polymer mixture. Preferably, theflow of material into and out of the first reactor is controlled tomaintain a relatively constant average molecular weight and narrowmolecular weight distribution of the polyalphaolefin, e.g., as reflectedby inherent viscosity. The resident time of the reactant mixture in thesecond reactor can be varied in accordance with the desired finalmolecular weight and molecular weight distribution of thepolyalphaolefin. The average molecular weight of the polyalphaolefins inthe reactant mixture in the second reactor tend to be far greater thanthat of the oligomer/polymer mixture in the first reactor. Additionalreactors can also be used, depending on the design of the system.

As mentioned above, the polymerization of the alpha olefin monomers isconducted in the presence of a catalyst system, which includes atransition metal catalyst and a co-catalyst mixture. The catalyst andco-catalysts may be added as initial raw ingredients or they may beadded as additives at any time during the polymerization process.Preferably, the catalyst and co-catalysts are added to thepolymerization reaction mixture at the same time alpha olefin monomersare added. Alternatively, in a two-stage process, the catalyst and theco-catalyst mixture are added at any time during actual polymerization,i.e., in the absence of “catalyst killers” or any otherpolymerization-terminating ingredient.

Preferably, the process is carried out in the presence of excessmonomers to provide a process which does not end due to the exhaustionof monomers. In a preferred embodiment, the process is halted by theaddition of deactivators, or catalyst inhibitors, such as a mixture ofisopropyl alcohol and butylated hydroxytoluene, after a sufficientamount of polyalphaolefin is produced by the polymerization reaction.The addition of the catalyst inhibitors terminates the polymerizationreaction in advance of full monomer conversion and provides selectivecapture of polyalphaolefins having the desired properties includingdesired molecular weight and molecular weight distribution. Isopropylalcohol may be added to the reactant mixture at a concentration of fromabout 0.1 weight percent to about 1 weight percent. Preferably, theisopropyl alcohol is added to the reactant mixture at a concentration ofabout 0.25 weight percent. Butylated hydroxytoluene may be added insmall amounts to the isopropyl alcohol as a preservative and/orantioxidant. Butylated hydroxytoluene may be added to the reactantmixture as a component mixture in the isopropyl alcohol at aconcentration of from about 0.1 weight percent to about 5.0 weightpercent of the isopropyl alcohol. Preferably, the butylatedhydroxytoluene is added to the reactant mixture at a concentration ofabout 1.0 weight percent of the isopropyl alcohol.

Preferably, the polymerization is carries out until the weight percentof the polyalphaolefin in the reactant mixture ranges from at leastabout 4 to about 12 weight percent polyalphaolefin. The weight percentof the polyalphaolefin in the reactant mixture more preferably rangesfrom at least about 5 to about 10 weight percent, and even morepreferably ranges from at least about 7 to about 10 weight percent.

In another specific embodiment, the process is carried out in theabsence of a hydrocarbon solvent until all available alpha olefinmonomers have been exhausted, i.e., polymerized. Due to the absence ofsolvent, after the alpha olefin monomers have been polymerized, apolyalphaolefin block is formed. “Polyalphaolefin block” is hereindefined as polyalphaolefin having a sufficiently high viscosity suchthat the polyalphaolefin is gel-like and may even retain itsthree-dimensional shape, e.g., a cylindrical block, at room temperature.The polyalphaolefin block is preferably a ductile or malleable masswhich is resilient and tacky. The polyalphaolefins which form thepolyalphaolefin block should be amorphous and substantiallynon-crystalline having an ultra-high molecular weight.

The polyalphaolefin block may then be used to reduce drag in a conduitby adding the polyalphaolefin block, or pieces of the polyalphaolefinblock, to a conduit containing hydrocarbons. The polyalphaolefin blockmay also be further processed by any method known to those skilled inthe art to be utilized to reduce drag in a conduit. For example, thepolymer block may be frozen using liquid nitrogen and ground intosmaller pieces which may then be directly combined with hydrocarbon in aconduit to reduce drag, or dissolved in an emulsifier or dispersant andthen combined with hydrocarbon in a conduit to reduce drag.

The flow diagram of FIG. 1 illustrates a batch polymerization systemused in one specific embodiment of the methods of the present invention.The system includes a catalyst preparation tank 10 and a batch reactionvessel 20. The catalyst preparation tank 10 includes a first inletstream 11 that includes the transition metal catalyst and a second inletstream 15 that includes a co-catalyst mixture. An appropriate mixing oragitation device 17 mixes the catalyst material with the co-catalystmixture to form a catalyst system 18. An outlet 16 in communication witha first inlet 21 of the batch reaction vessel 20. Valves, pumps andother devices (not shown) can be used to control the flows of thevarious streams. The batch reaction vessel 20 has a second inlet forintroduction of the alpha olefin monomer material in stream 22. Thebatch reaction vessel 20 also has a third inlet for the introduction ofthe hydrocarbon solvent in stream 23. In a specific embodiment of theinvention, wherein a viscosity-reducing agent is utilized, a fourthinlet is included for introduction of a viscosity reducing agent thatincludes a substantially hydrophobic dispersant. Aromatic and/oraliphatic hydrocarbon solvent may be introduced together with theviscosity reducing agent through inlet 24 or, alternatively, may beintroduced separately through inlet 23. Batch reaction vessel 20 canalso include an appropriate mixing or agitation device 19. In oneembodiment of the method, the catalyst system 18, prepared in thecatalyst preparation tank 10, is introduced to the batch reaction vessel20 through inlet 21 of the batch reaction vessel 20 and is mixed indesired proportions with the hydrocarbon solvent, viscosity reducingagent and alpha olefin material which are metered into the batchreaction vessel 20 through their respective inlets. Polymerization isinitiated at appropriate temperatures and pressures. Alternatively,polymerization may be initiated at appropriate temperatures andpressures prior to the introduction of the viscosity reducing agent, theviscosity reducing agent thereafter being introduced duringpolymerization. Polymerization may be terminated naturally when all themonomer in the reactor is consumed, or, alternatively, by introducing adeactivator. The polyalphaolefin malarial formed by the process ofpolymerization may be withdrawn from the batch reaction tank 20 throughinlet 26. Valves, pumps and other devices (not shown) may be interposedas necessary to remove the entire mixture, including formedpolyalplaolefin, from the batch reaction polymerization vessel.

In accordance with another embodiment of this invention, shown in FIG.2, a catalyst system 180 that includes a transition metal catalyst maybe prepared in a catalyst preparation and storage vessel 100 by mixingthe transition metal catalyst in stream 110, introduced through a firstinlet 111, with co-catalyst mixture in stream 150 introduced through asecond inlet 151 to form a catalyst system 180. The catalyst preparationand storage vessel may include a mixing or agitation device 170 asnecessary. The catalyst preparation and storage vessel 100 has outlet160 in communication with a first inlet 210 of a first reactor 200. Thecatalyst system 180 may be continuously metered from the catalystpreparation and storage vessel 100 through outlet 160 in communicationwith first inlet 210 into the first reactor 200 whereby the catalystsystem 180 is mixed in desired proportions with alpha olefin monomers instream 220 introduced through second inlet 221 and hydrocarbon solventstream 235, introduced through a third inlet 236, which are continuouslymetered from other sources not shown. Polymerization is initiated in thefirst reactor 200 at appropriate temperatures and pressures. Firstreactor 200 includes an appropriate mixing or agitation device 270 andan outlet 250 for continuous removal of polyalphaolefin and the othermaterials in the reactor 200. A viscosity reducing agent in stream 240,which includes a substantially hydrophobic dispersant, may also bemetered from a separate source into the first reactor 200 through afourth inlet 241 prior to commencing the polymerization reaction.Additionally, or alternatively, the viscosity reducing agent may bemetered into the first reactor 200 through the fourth inlet 241 duringpolymerization. Additional reactors may also be provided in whichpolymerization continues and from which non-crystalline, ultra-highmolecular weight polyalphaolefin product may be recovered.

In another specific embodiment, referring to FIG. 3, a second reactor300 is provided in which the materials of the first reactor 200 (alsoshown in FIG. 2), including catalyst system, unreacted alpha olefin,oligomers and polyalphaolefin, may be pumped continuously from outletstream 250 of the first reactor by pump 260 into the second reactor 300through inlet stream 310, where the molecular weight of thepolyalphaolefin drag reducing agent polymer is further increased.Additionally, a viscosity reducing agent in stream 240 may also bemetered into the second reactor 300 through fourth inlet 241. Secondreactor 300 includes an appropriate mixing or agitation device 370 andoutlet 380 for removal of the DRA product which includes polyalphaolefinand the other remaining materials in second reactor 300. Removal of thepolyalphaolefin and other remaining materials in reactor 300 may beaccomplished by pump 390. Valves, pumps and other devices (not shown)may be interposed as necessary. As another feature of this invention,fresh reactants may be added to the first reactor 200 as material isbeing pumped from the first reactor 200 to the second reactor 300. Thereaction may be terminated by introducing a deactivator (not shown) or,alternatively, the reaction may terminate naturally when all the monomerin the reactors are consumed. Preferably, excess alpha olefin monomersare present during polymerization and deactivator is added to thereactant mixture to halt polymerization once the non-crystalline,ultra-high molecular weight polyalphaolefin is formed. As an additionaloption and additional feature of this specific embodiment of theinvention, the reaction may be continued by forwarding the formedpolyalphaolefin and other remaining materials to a pressurized storagevessel (not shown) where the molecular weight of the formedpolyalphaolefin may yet be further increased. The polyalphaolefin dragreducing agent may be introduced into a conduit to reduce frictionalenergy losses of the material flowing through the conduit.

EXAMPLES

A series of tests was conducted to demonstrate the superior propertiesof drag reducing agents made in accordance with the invention. Some ofthose tests are discussed below.

Example 1

Four different drag reducing agents were compared for their ability toincrease flow of various hydrocarbons. For control purposes, all fourdrag reducing agents were formed from the same titanium trichloride[(TiCl₃)₃—AlCl₃—AKZO AA] as the transition metal catalyst. Each,however, was formed using a different co-catalyst mixture. Compositions“A” and “B” were polyalphaolefins made in accordance with the invention.Both were made using alkylaluminoxane as a co-catalyst. The co-catalystmixture used to make composition “A” was isobutylaluminoxane (IBAO) anddibutylaluminum chloride (DIBAC); while the co-catalyst mixture used tomake sample “B” was IBAO and diethylaluminum chloride (DEAC). Incontrast, compositions “C” and “D” are commercially available dragreducing compositions, and were already prepared. Compositions “C” and“D” were made without use of an alkylaluminoxane.

Composition “A” was formed using 212 weight ppm based upon the weight ofall the reactants in the reactant mixture of the same titaniumtrichloride [(TiCl₃)₃—AlC₁₃—AKZO—AA]. The titanium trichloride wascombined with 1,346 weight ppm isobutylaluminoxane (IBAO) and 851 weightppm DIBAC as co-catalysts to form a catalyst system. The catalyst systemwas combined with C₆ (64,800 weight ppm) and C₁₂ (64,800 weight ppm)alpha olefin monomers and a solvent (KOCH Sure-Sol-150, 857,991 weightppm) at a temperature of 10° C. in accordance with the invention andallowed to polymerize to form ultra-high molecular weightpolyalphaolefins.

Composition “B” was formed using 300 weight ppm based upon the weight ofall the reactants in the reactant mixture of the same titaniumtrichloride [(TiCl₃)₃—AlCl₃—AKZO—AA]. The titanium trichloride wascombined with 1,657 weight ppm isobutylaluminoxane (IBAO) and 1,093weight ppm DEAC as co-catalysts to form a catalyst system. The catalystsystem was combined with C₈ (39,500 weight ppm) and C₁₄ (39,500 weightppm) alpha olefin monomers and a solvent (KOCH Sure-Sol-150, 907,950weight ppm) at a temperature of −5° C. in accordance with the inventionand allowed to polymerize to form ultra-high molecular weightpolyalphaolefins.

Each of the four DRA compositions (A-D) was measured for Percent FlowIncrease, using three “test hydrocarbons,” namely, Alaska North Slopecrude oil (ANS), Bow River crude oil (BOW RIVER), and hexane. The BOWRIVER test hydrocarbon was a highly viscous crude oil from the IPLPipeline in Canada. One inch (1″) and ¼″ hydraulic flow loops were used.The ¼″ flow loop was used for the hexane. The 1″ flow loop was used totest the ANS crude oil and BOW RIVER crude oils, which are so viscousthat they do not generate turbulent flow in a ¼″ flow loop. Each DRAcomposition was combined with one gallon of each of the testhydrocarbons, forming a total of twelve (12) DRA test samples. Each DRAtest sample was added to 24 gallons of the corresponding testhydrocarbon and passed through the flow loop over a constant timeinterval based upon the total weight of the DRA test sample andcorresponding test hydrocarbon. In accordance with the Percent FlowIncrease test, the weight of each test hydrocarbon (with DRA) passingthrough the flow loop over a constant time interval was measured, andcompared to the baseline weight of each test hydrocarbon (without DRA)passing through the same flow loop over the same constant time interval.Percent Flow Increase for each DRA composition was measured. Asreflected in Tables I and II, the Percent Flow Increase for inventioncompositions “A” and “B” was substantially higher than the Percent FlowIncrease for comparative compositions “C” and “D.” For example, whenplaced in hexane, invention compositions “A” showed 48% improvement inPercent Flow Increase over that of Composition “D.” Even moresurprising, and also indicative of the superior drag reducingcapabilities of the present invention in an actual commercial setting,Compositions “A” and B both increased the flow rate of BOW RIVER crudeoil while neither compositions “C” nor “D” were able to increase theflow of the BOW RIVER crude oil.

TABLE I PERCENT FLOW INCREASE DRA ANS @ 3 ppm BOW RIVER @ 4.6 ppm HEXANE@ 1 ppm A 15.0 3.0 40.1 B 12.0 5.5 37.5 C¹ 10.8 −0.5 31.1 D² — 0.0 27.1¹LIQUID POWER ™ commercial DRA from Conoco Inc. ²FLO-1005 ™ commercialDRA from Baker-Hughes, Inc.

TABLE II IMPROVEMENT IN PERCENT FLOW INCREASE FOR DRA “A” AND DRA “B INHEXANE @ 1 ppm Comparison Percent Improvement in Percent Flow Increase Acompared to C 28.9 A compared to D 48.0 B compared to C 20.6 B comparedto D 38.4

Example 2

Additional tests were conducted, again, to compare the drag reducingproperties of the invention, made using alkylaluminoxane co-catalysts,with the drag reducing properties of commercial DRA compositions, madewithout alklylaluminoxaiie co-catalysts. These tests were conducted overa range of concentrations. As discussed below. the results wereimpressive.

Again, for control purposes, all four drag reducing agents were formedusing the same transition metal catalyst, i.e., titanium trichloride[(TiCl₃)₃ —AlCl₃—AKZO Type D], but different co-catalyst mixtures. Theco-catalyst mixture for composition “E” was isobutylaluminoxane (IBAO)and dibutylaluminum chloride (DIBAC). The co-catalyst mixture forcomposition “F” was IBAO and diethylaluminum chloride (DEAC).

Composition “E” was formed using 212 weight ppm based upon the weight ofall the reactants in the reactant mixture of the same titaniumtrichloride [(TiCl₃)₃—AlCl₃—AKZO—AA]. The titanium trichloride wascombined with 1,346 weight ppm isobutylaluminoxane (IBAO) and 851 weightppm DIBAC as co-catalysts to form a catalyst system. The catalyst systemwas combined with C₆ (64,800 weight ppm) and C₁₂ (64,800 weight ppm)alpha olefin monomers and a solvent (KOCH Sure-Sol-150, 857,991 weightppm) at a temperature of 10° C. in accordance with the invention andallowed to polymerize to form ultra-high molecular weightpolyalphaolefins.

Composition “F” was formed using 300 weight ppm based upon the weight ofall the reactants in the reactant mixture of the same titaniumtrichloride [(TiC₃)₃—AlCl₃—AKZO—AA]. The titanium trichloride wascombined with 1,657 weight ppm isobutylaluminoxane (IBAO) and 1,093weight ppm DEAC as co-catalysts to form a catalyst system. The catalystsystem was combined with C₈ (39,500 weight ppm) and C₁₄ (39,500 weightppm) alpha olefin monomers and a solvent (KOCH Sure-Sol-150, 907,950weight ppm) at a temperature of −5° C. in accordance with the inventionand allowed to polymerize to form ultra-high molecular weightpolyalphaolefins.

Comparative compositions “G” and “H” were both made using co-catalyststhat included diethylaluminum ethoxide. The tests were conducted using a1/4″ flow loop in the same manner described above, with hexane as thetest hydrocarbon in all cases. Percent Drag Reduction (% DR) was thebasis for comparison.

Results are indicated in Tables III and IV. At the low end of theconcentration range (0.5 ppm), the percent drag reduction was 27 and26.6, respectively, for invention compositions “E” and “F.” At that sameconcentration, the percent drag reductions for comparative compositions“G” and “H” were 13.7 and 18. Thus, at that concentration the inventionDRAs improved drag reduction by almost 100% over the comparative DRAs.Even at higher concentrations (e.g., at 2.0 ppm), the invention DRAsstill provided superior drag reduction. At DRA concentrations of 2.0ppm, for example, compositions “E” and “F” still provided as much as21.7% more drag reduction compared to compositions “G” and “H.”Referring to FIGS. 4-7, it can be seen that over 2.0 ppm of thecomparative drag reducing compositions (see compositions “E” and “F” inFIGS. 6 and 7 at 2.0 ppm) is required to achieve the same percent dragreduction provided by 1.0 ppm of the invention DRA (see compositions “C”and “D” in FIGS. 4 and 5). Based on those data, over twice as muchnon-invention DRA might be required to achieve the same level of dragreduction as invention DRA.

TABLE III PERCENT DRAG REDUCTION Concentration of DRA DRA Composition0.5 ppm 1.0 ppm 2.0 ppm E (FIG. 4) 27.0 43.0 47.1 F (FIG. 5) 26.6 42.646.3 G¹ (FIG. 6) 13.7 26.0 38.7 H² (FIG. 7) 18.0 32.3 41.8 ¹LIQUIDPOWER ™ commercial DRA from Conoco Inc. ²FLO-1005 ™ commercial DRA fromBaker-Hughes, Inc.

TABLE IV PERCENT INCREASE IN DRAG REDUCTION Concentration of DRAComparison 0.5 ppm 1.0 ppm 2.0 ppm E compared to G 97.1 63.8 21.7 Ecompared to H 50.0 33.1 12.7 F compared to G 94.2 63.8 19.6 F comparedto H 47.8 31.9 10.7

Example 3

In another specific embodiment of the invention, a drag reducing agentmade using ethylene dichloride as a co-catalyst was prepared. This dragreducing agent, Composition “I”, was formed using ethylene dichlorideand isobutylaluminoxane as the co-catalysts.

Composition “I” was formed Lsing 260 weight ppm based upon the weight ofall the reactants in the reactant mixture of the same titaniumtrichloride [(TiCl₃)₃—AlCl₃—AKZO—AA] as used in Examples 1 and 2. Thetitanium trichloride was combined with 2.815 weight ppmisobutylaluminoxane (IBAO) and 96 weight ppm ethylene dichloride asco-catalysts to form a catalyst system. The catalyst system was combinedwith C₈ (59,230 weight ppm) and C₁₄ (59,230 weight ppm) alpha olefinmonomers and a solvent (KOCH Sure-Sol-150, 868,368 weight ppm) at atemperature of −5° C. in accordance with the invention and allowed topolymerize to form ultra-high molecular weight polyalphaolefins.

Composition “I” was compared to Compositions “G” and “H” of Example 2 todetermine the effect using ethylene dichloride as a co-catalyst has ondrag reduction. Composition “I” was also compared to Compositions “E”and “F” of Example 2 to determine the effect using ethylene dichlorideas a co-catalyst has on polymerization time, i.e., the rate ofpolymerization of the alpha olefin monomers.

Composition “I” was measured for percent drag reduction by placingComposition “I” in hexane in a ¼″ hydraulic flow loop as described inExample 1. Percent drag reductions are shown in Table V and percentincreases in drag reduction are shown in Table VI. The rate ofpolymerization was determined by measuring the amount of time necessaryfor the polymerization reaction to form 5 weight percent polyalphaolefinbased upon the total weight of the reactant mixture. The rates ofpolymerization are shown in Table VII.

TABLE V PERCENT DRAG REDUCTION IN HEXANE @ 1 ppm DRA Composition % DR G(FIG. 6) 26.0 H (FIG. 7) 32.3 I (FIG. 8) 34.7

TABLE VI PERCENT INCREASE IN DRAG REDUCTION Comparison % increase Icompared to G 33.5 I compared to H 7.4

TABLE VII POLYMERIZATION RATE TO FORM 5 wt % POLYALPHAOLEFIN DRAComposition Hours E 22 F 36+¹ I 4.1 ¹Polymerization was terminated at 36hours and polyalphaolefin concentration was 4 wt %.

As reflected in Tables VI and VII, Composition “I” provided not onlysuperior drag reduction, but also a polymerization rate at least 3 timesfaster, when compared to drag reducing agents which do not utilizeethylene dichloride as a co-catalyst. As shown in Table VI, the percentdrag reduction at 1 ppm DRA was 34.7 for invention Composition “I”compared to 26.0 and 32.3 for Compositions “G” and “H” respectively.Thus, at 1 ppm the invention DRA improved drag reduction by as much as33% over the comparative DRAs.

Composition “I” also provided an effective drag reducing agent within ashorter period of time. In other words, by using ethylene dichloride asa co-catalyst, the polymerization rate increased at least three fold. Asillustrated in Table VII, 5 weight percent polyalphaolefin based uponthe total weight of the reactant mixture was formed in slightly morethan 4 hours. Polymerization of alpha olefin monomers without usingethylene dichloride took at least 15 hours to from 15 weight percentpolyalphaolefin.

These results show that Composition “I” is a superior drag reducingagent compared to drag reducing agents which are formed without usingethylene dichloride as a co-catalyst. These results further show thatComposition “I” is formed at a rate of polymerization which is 3 to 4times faster than the polymerization time necessary to form dragreducing agents which are not formed using ethylene dichloride.Accordingly, by using ethylene dichloride as a co-catalyst to from thedrag reducing agents of the invention, the rate of polymerization can beincreased, while providing a drag reducing agent which is superior toother drag reducing agents.

From these examples, it can be seen that the at least certainembodiments of the present invention provide superior properties whencompared to other drag reducing agents. As mentioned above, while theexamples reflect specific embodiments of the invention, the followingclaims, including their equivalents, will define the scope of theprotected invention.

What is claimed is:
 1. A process for forming a drag reducing agentcomprising a non-crystalline, ultra-high molecular weightpolyalphaolefin having an inherent viscosity of at least about 10deciliters per gram, the process comprising: contacting alpha olefinmonomers with a catalyst system in a reactant mixture, wherein thecatalyst system includes a non-metallocene transition metal catalyst and-an alkylaluminoxane co-catalyst; and polymerizing the alpha olefinmonomers at a temperature at about or less than 25° C., wherein duringthe polymerization, at least a portion of the alpha olefin monomerspolymerize in the reactant mixture to provide a non-crystalline,ultra-high molecular weight polyalphaolefin.
 2. The process of claim 1,wherein the polymerization is terminated by adding a deactivator to thereactant mixture after at least a portion of the alpha olefin monomerspolymerize in the reactant mixture to provide the non-crystalline,ultra-high weight polyalphaolefin.
 3. The process of claim 2, whereinthe deactivator includes a mixture of isopropyl alcohol and butylatedhydroxytoluene.
 4. The process of claim 1, wherein the non-metallocenetransition metal catalyst includes titanium trichloride.
 5. The processof claim 1, wherein the alkylaluminoxane includes methylaluminoxane orisobutylaluminoxane.
 6. The process of claim 1, wherein the catalystsystem includes diethylaluminum chloride or dibutylaluminum chloride. 7.The process of claim 1, wherein the alpha olefin monomers comprisehomopolymers, terpolymers or copolymers.
 8. The process of claim 1,wherein the alpha olefin monomers comprise co-polymers of 1-hexene and1-dodecene alpha olefins or co-polymers of 1-octene and 1-tetradodecenealpha olefins.
 9. The process of claim 1, wherein the reactant mixtureincludes at least one hydrocarbon solvent.
 10. The process of claim 9,wherein the alpha olefin monomers and polyalphaolefin remainsubstantially dissolved in the hydrocarbon solvent duringpolymerization.
 11. The process of claim 1, wherein the polymerizationof the alpha olefin monomers continues such that polyalphaolefin ispresent in the reactant mixture at a concentration of at least about 4weight percent based upon the weight of the reactant mixture and thepolyalphaolefin having an inherent viscosity of at least about 10deciliters per gram is formed in less than about 12 hours.
 12. A processfor reducing drag in a conduit, comprising: forming a drag reducingagent wherein the drag reducing agent includes a non-crystalline,ultra-high molecular weight polyalphaolefin, is formed by contactingalpha olefin monomers with a catalyst system in a reactant mixture,wherein the catalyst system includes a transition metal catalyst and analkylaluminoxane co-catalyst; polymerizing the alpha olefin monomers ata temperature at about or less than 25° C.; wherein during thepolymerization, at least a portion of the alpha olefin monomerspolymerize in the reactant mixture to provide a non-crystalline,ultra-high molecular weight polyalphaolefin having an inherent viscosityof at least 10 deciliters per gram; and introducing the drag reducingagent into the conduit.
 13. The process of claim 12 wherein the dragreducing agent provides a flow increase of at least about 30% when thepolyalphaolefin is present in hexane at a weight concentration of 1 partper million.
 14. The process of claim 12, wherein drag is reduced atleast about 30% when the polyalphaolefin is present in hexane at aweight concentration of 1 part per million.
 15. A process for forming adrag reducing agent comprising a non-crystalline, ultra-high molecularweight polyalphaolefin having an inherent viscosity of at least about 10deciliters per gram, the process comprising: contacting alpha olefinmonomers with a catalyst system in a reactant mixture, wherein thecatalyst system includes a non-metallocene transition metal catalyst anda co-catalyst mixture, the co-catalyst mixture having at least twoco-catalysts wherein one of the two co-catalysts is a halohydrocarbon;polymerizing the alpha-olefin monomers at a temperature at about or lessthan 25° C., wherein during the polymerization, at least a portion ofthe alpha olefin monomers polymerize in the reactant mixture to providea non-crystalline, ultra-high molecular weight polyalphaolefin.
 16. Theprocess of claim 15, wherein the halohydrocarbon is a chloridecontaining halohydrocarbon.
 17. The process of claim 16, wherein thechloride containing halohydrocarbon is ethylene dichloride.
 18. Theprocess of claim 15, wherein the transition metal catalyst comprisestitanium trichloride.